The present invention relates to a cutting machine for cutting a workpiece such as a semiconductor wafer and, more specifically, to a cutting machine capable of cutting a workpiece at a tilt angle to the plane perpendicular to the surface of the workpiece.
In the production of a semiconductor device, for example, the front surface of a substantially disk-like semiconductor wafer is divided into a plurality of rectangular areas by cutting lines called xe2x80x9cstreetsxe2x80x9d arranged in a lattice form, and a predetermined circuit pattern is formed in each of the rectangular areas. The plurality of rectangular areas having a circuit pattern are cut and separated from one another to form so-called semiconductor chips. The semiconductor wafer is cut by a precision cutting machine called xe2x80x9cdicing machinexe2x80x9d.
The above cutting machine comprises a spindle unit having a spindle housing, a rotary spindle rotatably supported by the spindle housing and a cutting blade attached to the end of the rotary spindle and cuts a workpiece held on a chuck table along predetermined cutting lines by moving the workpiece relative to the cutting blade while rotating the cutting blade at a high speed. In this cutting machine, the cutting blade is generally positioned perpendicular to the workpiece holding face of the chuck table and therefore, the cut surface of the workpiece is formed perpendicular to the front surface and the back surface of the cut semiconductor chip.
By the way, in the step of mounting a glass diode having a rectangular shape as a semiconductor chip on a semiconductor device, care must be taken not to place the cut surface of the glass diode on the semiconductor device. That is because, when the cut surface of the semiconductor chip is perpendicular to its front surface as described above, the cut surface of the semiconductor chip is liable to be placed on the semiconductor device. To solve this problem, there is proposed a semiconductor chip whose cut surface is formed at a tilt angle with the plane perpendicular to its front surface.
In order to cut the semiconductor wafer at a tilt angle with the plane perpendicular to its front surface as described above, the cutting blade must be inclined with respect to the workpiece holding face of the chuck table. As a technology for inclining the cutting blade with respect to the workpiece holding face of the chuck table, there is employed a method of holding a workpiece on a chuck table by interposing a tilting jig therebetween.
However, according to the method of holding a workpiece on a chuck table with a tilting jig interposed therebetween as described above, the alignment step for detecting an area to be cut of the workpiece is difficult to carry out because the workpiece is held in an inclined state. Further, in the method of holding a workpiece on a chuck table with a tilting jig interposed therebetween, when the cutting direction is to be changed by 90xc2x0, the workpiece must be re-placed relative to the tilting jig. This work is troublesome and reduces productivity.
It is an object of the present invention to provide a cutting machine which make it easy to carry out the alignment step for detecting an area to be cut of a workpiece held on a chuck table, and makes it possible to cut the workpiece at a tilt angle to the plane perpendicular to the surface of the workpiece without re-placing it when the cutting direction is changed by 90xc2x0.
To attain the above object, according to the present invention, there is provided a cutting machine comprising a chuck table having a workpiece holding face for holding a workpiece, a spindle unit having a rotary spindle for mounting a cutting blade which cuts the workpiece held on the chuck table, and a spindle unit support mechanism for supporting the spindle unit in such a manner that it can move in a cutting direction perpendicular to the workpiece holding face, wherein
the spindle unit support mechanism comprises a movable base which is movably disposed in a cutting direction perpendicular to the workpiece holding face, a guide rail which is provided on the side face of the movable base and has a predetermined curvature radius, a spindle unit support member which is movably disposed along the guide rail and mounts the spindle unit, and an angle adjustment mechanism for moving the spindle unit support member along the guide rail to adjust the angle.
It is desired that the center of the curvature radius of the above guide rail be set to the cutting blade mounting portion of the above rotary spindle. The above angle adjustment mechanism comprises a male screw rod turnably supported to the movable base and a movable female screw block to be screwed to the male screw rod and to be engaged with the spindle unit support member, and the spindle unit support member engaged with the movable female screw block is moved along the above guide rail by turning the male screw rod to move the movable female screw block along the male screw rod. Further, the above angle adjustment mechanism comprises an angle setting block which is selectively and detachably mounted to the movable base and has a support face for placing the spindle unit thereon and supporting it.